It appears this wasn't simply a matter of Hamoui cashing in on the sale and quitting. AdMob employees are struggling to negotiate the corporate structure at Google.

"They have real frustration," says our source. For example, if AdMob wants to introduce a new product, it has to get a variety of departments at Google to "buy-in" to the idea.

We've heard this big-company complaint about Google before. Lars Rasmussen, cofounder of Google Maps, left for Facebook citing the fact that Google is too big now.

Hamoui leaving Google is a "big loss," says our source.

Hamoui turned AdMob into a leader in advertising in apps, when Google and other companies were more focused on advertising on the mobile web. Losing a sharp mobile ad exec just as the mobile world catches on fire has to hurt Google.

"This is not what Google wanted. Google would much, much rather have Omar stay," speculates our source.

We've reached out to Hamoui and Google, but we received no response. If we hear anything noteworthy, we'll update you. If you have heard anything, email us at jyarow@businessinsider.com.